1. Field of the Invention
The present invention relates to a method and apparatus for transmitting data over a wireless local area network (hereinafter referred to as a ‘WLAN’) mesh network, in which in data transmission over a WLAN mesh network, a data transmission time for providing data service requiring the real-time property is variably controlled step-by-step, enabling efficient data transmission.
This work was supported by the IT R & D program of MIC/IITA [2006-S-061-02, “R&D on Router Technology for IPv6 based QoS Services and Host Mobility”].
2. Description of the Related Art
In existing WLAN equipments, a distributed coordination function (hereinafter referred to as a ‘DCF’) function and a point coordination function have been defined and used in order to share a medium. Such equipments were adapted to transmit data through specific contention, but were problematic in that they had low data transmission efficiency and a high data error rate because collision according to data transmission frequently occurred.
Due to the problems, a collision avoidance scheme employing a control frame was proposed and, therefore, the occurrence of collision was decreased significantly. However, the collision avoidance scheme had a lot of problems in providing data requiring the real-time property, such as multimedia stream data.
Thus, grades were assigned to transmission of data in order to prioritize the transmission of data. In this case, such a central control method was accompanied by an abrupt increase in load on a central management system and a managerial difficulty. Even in the case in which the transmission of data is distributed and processed, there was limit to QoS (Quality of Service) guarantee of data.
In particular, although data is given a priority and transmitted, if there is transmission of a frame having an excessive priority, a problem arises because it is difficult to guarantee QoS with respect to data that has already been transmitted and serviced due to transmission of excessive data.
That is, although a priority frame is excessive when transmitting the priority frame, the priority frame cannot be controlled or processed. Accordingly, not only the transmission of the priority frame is delayed significantly or limited, but there is limit to QoS guarantee with respect to the priority frame.
There is also limit to frames with a low priority due to transmission on the basis of a priority frame.